Conventionally, positron emission computed tomography (PET) apparatuses are known as nuclear medicine imaging apparatuses that can make a functional diagnosis in body tissues of a subject.
Specifically, in a PET examination, a compound labeled with a positron-emitting radionuclide is administered to the subject. Such a PET apparatus coincidentally counts a pair of gamma rays (pair annihilation gamma rays) of 511 keV emitted in approximately opposite directions when a positron emitted from the labeled compound binds to an electron and annihilates by using a photon counting detector arranged around the subject. The PET apparatus then performs calculation processing on data of the gamma rays coincidentally counted (coincidence counting information) to reconstruct a PET image.
More specifically, the PET apparatus collects counting information including the detection position of the gamma rays, the detection time (e.g., clock time of detection) of the gamma rays, and the energy value of the gamma rays from counting results output by the detector. The nuclear medicine imaging apparatus then generates a combination of two pieces of counting information whose detection time is within predetermined duration as the coincidence counting information obtained by counting pair annihilation gamma rays nearly coincidentally. The PET apparatus then reconstructs a PET image indicating distribution of the labeled compound in the way that the labeled compound emitting the positron is present on a line connecting the detection positions included in each piece of the counting information constituting the coincidence counting information.
Furthermore, in recent years, PET-CT apparatuses in which a PET apparatus and an X-ray computed tomography (CT) apparatus that supplies form information are integrated have been in practical use.
As a result of supplement of the counting information in excess of the processing capacity of the PET apparatus, the counting information may be discarded.